All Draw Curiosity videos are fully subtitled in English and Spanish. The blog post builds on the concepts touched upon in the video.

I hope you enjoyed this video! I had loads of fun crafting and designing it – I never expected blurry eyes, cameras and cuttlefish to be related in any way! So… let’s dig a little bit deeper into some of the concepts covered in the video:

How do certain drugs cause the pupil to dilate?

The scientific term is known as ‘mydriasis’. Certain medications cause the pupil to dilate by blocking the muscarinic acetylcholine receptors in the eye, removing their ability to respond to light. The radial fibres found in the iris, are forced to contract, leading them to increase the aperture of the eye. There are drugs used specifically by opticians to induce pupil dilation, but many other medications, including anticholinergics and those that affect the serotonin levels in the brain also have the ability to affect the iris’ response to light.

How can I take beautiful bokeh pictures?

Bokeh is the term in photography which relates to subject isolation, meaning that the subject of the photograph is in focus, whereas the background is out of focus, creating an aesthetically pleasing effect.

There are two main techniques I use to take pictures with a beautiful blurry background:

• Open the aperture wide. The lower you can stop the F-stop on your camera, the wider the aperture and the more light will enter the camera. This narrows the depth of field, which is the volume in focus to the camera. By focusing the depth of field on your subject, you can easily isolate it from the background, and the wider the aperture and better the quality of your lens, the softer and blurrier the background will be.

  

• Zoom in. Lenses which zoom in more tend to generate a similar effect.

  

Do cephalopods really see like that?

In theory, no one knows, in the same way none of us know how anybody else sees, and whether the way we see is the same. However, my reconstruction is based upon my interpretation of the literature on cephalopod vision, and particularly by the research carried out by Stubbs & Stubbs which you can read in depth here: “A Novel Mechanism for Color Vision: Pupil Shape and Chromatic Aberration Can Provide Spectral Discrimination for Color Blind Organisms” by Stubbs & Stubbs 2015

Why do they see the world that way?

Although cephalopods and humans share a similar camera shaped eye, the way it is designed to detect and discriminate the world is adapted in very different ways. The main features that distinguish their eyes from ours is the fact that they have a single photoreceptor type, a U or W-shaped pupil and a very fast focusing lens.

Humans can detect colour using photochemistry, which integrates the signal of three specialised photoreceptors, also known as the cones. Cephalopods only have one, meaning in theory they are only capable of perceiving shades of grey. However, rather than relying on specialised chemistry, they use physics to split the light into its constituent wavelengths, much like a prism, and focusing each one on a different area on the back of their eye.

They do this due to the shape of their pupil. Pupils that allow light to enter off centre, such as extremely dilated circular pupils, or their own U or W-shaped pupils, are capable of affecting light in that way. In fact, the unique shape of their pupil means that regardless of the light conditions present, light always enters off-axis and thus always has this effect at the back of their eye.

Additionally, their lenses focus much faster than our own, so they are able to swivel across the different wavelength spectra to analyse their surroundings. It is unknown what cognitive process may follow this, and whether they may be capable of stacking the different slices and perceiving them as colour or not.

Why do cephalopods see better in low light conditions?

Cephalopods have a single photoreceptor type, whereas we have several. Our retinas are lined with rods and cones. The former are sensitive to a large spectrum of light wavelengths, meaning that detecting light at any of these wavelengths sends a message to the brain. Cones, which detect colour, have a much more reduced window of sensitivity. There are three types of cones, red, blue and green; which reflect the colours they are most sensitive to. Depending on the cones which are activated in certain areas of the retina, the brain is able to construct the colour which is being seen. However, due to the reduced sensitivity, a lot more light is necessary to adequately stimulate the cones and receive a colour signal. This is why in low light conditions we only see in black and white, because our rods are sensitive to a much wider spectrum of wavelengths. If our entire retina was lined with rods, rather than rods and cones, our sensitivity would be much better and we would likely have fantastic night vision. This is the principle the cephalopods are exploiting, all of their photoreceptors are sensitive to a wide spectrum of wavelengths, allowing them to see clearly at low light levels at the bottom of the ocean.

If you would like even more in-depth information, please don’t hesitate to comment – there is so much more to be said on these topics!

I hope you enjoyed and learned something new today! Let me know what you think in the comments – I would love to know! If you enjoyed this blog and would like to be notified of new entries, consider signing up to the mailing list here and subscribing to the YouTube channel!